OAKLAND (KPIX 5) — Oakland city officials said they are launching an investigation after a former police officer on disability was identified as the FBI agent who killed an associate of a suspect in the Boston Marathon bombing.

Aaron McFarlane, 41, fatally shot Ibragim Todashev in Florida last May. Todashev was an associate of Tamarlan Tsarnaev, one of the two men accused of planting bombs at the finish line of the 2013 marathon.

McFarlane retired from the Oakland Police Department in 2004 for medical reasons. For the past 10 years, he has collected more than $500,000 in tax-free disability pension payments, most of it public money.

KPIX 5 has learned from a source in the department that when McFarlane retired from OPD, he was facing the possibility of being fired. Instead, he opted for a medical retirement.

Even on disability, McFarlane was able to pass a FBI physical. On the FBI’s website, the agency said candidates “must be in excellent physical condition with no disabilities which would interfere in firearm use, raids, or defensive tactics.”

Oakland spokesperson Karen Boyd told KPIX 5 that “The City of Oakland is investigating the matter and will take further actions as appropriate.”

The City of Oakland could choose to take a number of actions, including referring the case to the district attorney.